Add a dummy CircleCI config to gh-pages branch (#602)

diff --git a/docs/circle.yml b/docs/circle.yml
new file mode 100644
index 0000000..e3ffd29
--- /dev/null
+++ b/docs/circle.yml
@@ -0,0 +1,3 @@
+test:
+  override:
+    - echo "test"